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Old 09-25-2012, 09:53 AM   #1
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Dyno results!!

I finally dynoed my car!

HP was 244 @ 6300; TQ was 212 @ 5600
with 15% drive train loss, that would figure to 287FWHP. Not bad.
FWIW, the air/fuel ratio looked a bit lean. Any insights?
3.2L engine
Softronic flash
75mm 996TB
Pedro's TechnoTorque 3
3" intake tubing to a cone filter located outside the engine compartment
Chinese headers
Fabspeed bypass pipes
Borla muffler (It's over 95db)
LW flywheel
Stage 3 plus clutch
Guard torque biasing diff
RSS underdrive pulley
A/C delete

** I also weighed her last week and she came in right at 2700 lbs!!!
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Old 09-25-2012, 10:52 AM   #2
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2700! How did you do that?

I noticed my exhaust crackling quite a bit more after loading the softronic flash. My first impression was ...ooh is that a little too lean?

What AFRs do you have? It hard to read your chart.
You could load up the stock flash and see if that brings you back. I have not tried this myself
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Old 09-25-2012, 11:15 AM   #3
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I got down to 2700 by:
removing the convertible top, motor, transmissions, and everything else related to the top (got a hard top for driving to and from events)
removing all the carpet
removing all sound deadening
swapping the seats for fiberglass shells (fixed to the floor w/ no adjustments)
radio delete
A/C delete including all pipes and condensors
fiberglass trunklid
removing the automatic spoiler & motor
carbon fiber hood
Borla muffler/cat bypass pipes/headers
LW flywheel
removing all carpet from front & rear trunks
lighter battery

....so now I'm autocrossing in F Prepared
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Old 09-25-2012, 11:21 AM   #4
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The first time I dynoed the car, it was also lean, and that was before the Softronic flash.
Funny, there's no indication of detonation despite the reading. I've raced the car like this all year. 155,000 miles and she keeps on running.
The readings looked around 18:1below 4K RPM, but then they improved to 14:1 above that.
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Old 09-25-2012, 11:34 AM   #5
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what maf housing are you using in that setup? if you've got any maf-related fault codes and the car is defaulting to the throttle position to determine airflow, the larger throttle body will mess up your trims.
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Old 09-25-2012, 12:19 PM   #6
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I cut the MAF housing from the original airbox. The car isn't throwing any codes, and it has a new MAF and 4 new O2 sensors.
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Old 09-25-2012, 01:12 PM   #7
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Interesting, given that time and time again it's been said that there is little in the way of "real HP gains to be had by tweaking the exhaust, especially with cheap Chinese eBay headers and bypass pipes. Are you running without cats?
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Old 09-25-2012, 02:14 PM   #8
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They're not likely getting a good exhaust sample on the dyno at lower RPM's. The car wouldn't actually run if it was at 18:1. The probe is probably too short and getting reversion at lower RPM's. They could put the dyno O2 sensor directly in the exhaust if you have a spare bung in the headers or bypass tubes.
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Old 09-25-2012, 03:00 PM   #9
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Glad to know that about the O2 sensor
...yes, no cats.
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Old 09-25-2012, 05:58 PM   #10
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They're not likely getting a good exhaust sample on the dyno at lower RPM's. The car wouldn't actually run if it was at 18:1. The probe is probably too short and getting reversion at lower RPM's. They could put the dyno O2 sensor directly in the exhaust if you have a spare bung in the headers or bypass tubes.
Are you guessing or have you seen data to support this? 18:1 is not really that lean in terms of efficiency ratios. I run a large displacement flat four with a fuel and ignition system far less sophisticated than those in our Porsches at efficiency ratios approaching that level. Some of the new direct injection engines run at 60:1 or more under certain conditions.
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Old 09-25-2012, 07:06 PM   #11
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Is there a stock Boxster S run on this same dyno to compare? I've seen too much variation between different dynos to hold too much faith in the power gains (though I hope they are real!)
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Old 09-26-2012, 02:37 AM   #12
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Originally Posted by shadrach74 View Post
Interesting, given that time and time again it's been said that there is little in the way of "real HP gains to be had by tweaking the exhaust, especially with cheap Chinese eBay headers and bypass pipes. Are you running without cats?


Seems to only be repeated by those who have the equation Chinese = crap drilled into their heads. My China headers were T304 stainless and they gave the 986 a true HP boost and an upper register snarl as awesome as any car. Simply stated the underpulley and headers IMO were the best two 986 mods.
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Old 09-26-2012, 05:58 AM   #13
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Quote:
Originally Posted by shadrach74 View Post
Are you guessing or have you seen data to support this? 18:1 is not really that lean in terms of efficiency ratios. I run a large displacement flat four with a fuel and ignition system far less sophisticated than those in our Porsches at efficiency ratios approaching that level. Some of the new direct injection engines run at 60:1 or more under certain conditions.
Ummm, not if it's running gasoline. 18:1 is way to lean to be safe for full power applications and would not be making good hp numbers. I suspect the exhaust sensor was fouled. Ultra lean burn on direct injection motors is useful at idle or cruising down hill, not making max power on a dyno.
http://en.wikipedia.org/wiki/Gasoline_direct_injection

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Old 09-26-2012, 07:31 AM   #14
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Hmmm well you learn something everyday.....I had thought anything approaching 16 was way too lean. Perhaps I am over "conditioned from blowing up 2 cycle motor cycle engines
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Old 09-26-2012, 07:37 AM   #15
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Originally Posted by j.fro View Post
I got down to 2700 by:
removing the convertible top, motor, transmissions, and everything else related to the top (got a hard top for driving to and from events)
removing all the carpet
removing all sound deadening
swapping the seats for fiberglass shells (fixed to the floor w/ no adjustments)
radio delete
A/C delete including all pipes and condensors
fiberglass trunklid
removing the automatic spoiler & motor
carbon fiber hood
Borla muffler/cat bypass pipes/headers
LW flywheel
removing all carpet from front & rear trunks
lighter battery

....so now I'm autocrossing in F Prepared
Nice now I get it! The two lids would really contribute to this ........how do you flip your lid once you get to an event? Do you have an extra set of hands
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Old 09-26-2012, 10:16 AM   #16
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Yeah, searching for someone to help remove the top is now a ritual at AX events...there are a few folks who volunteer knowing I'm gonna ask! Thank goodness everyone's pretty nice.
When the top is off and I'm out working the course, I get noticeably nervous if clouds begin to gather!
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Old 09-26-2012, 11:51 AM   #17
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Dyno on Youtube

And the dyno video...
Rennzenn Boxster screaming on the Dyno - YouTube
I had never heard my own car from outside the driver's seat. She's pretty loud!
I didn't hear any detonation during any of the Dyno runs.

Last edited by j.fro; 09-27-2012 at 01:55 AM.
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Old 09-26-2012, 12:49 PM   #18
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Yeah, searching for someone to help remove the top is now a ritual at AX events...there are a few folks who volunteer knowing I'm gonna ask! Thank goodness everyone's pretty nice.
When the top is off and I'm out working the course, I get noticeably nervous if clouds begin to gather!
We have this guy up here who created an open topped 944 track car....with a big mother of a wing; even the windscreen is gone....it's always raining. He waits for the grid to be released and then pulls out from his motor home awning! Keep a tarp handy or keep moving!! Haha
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Old 09-26-2012, 12:57 PM   #19
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Ummm, not if it's running gasoline. 18:1 is way to lean to be safe for full power applications and would not be making good hp numbers. I suspect the exhaust sensor was fouled. Ultra lean burn on direct injection motors is useful at idle or cruising down hill, not making max power on a dyno.
Gasoline direct injection - Wikipedia, the free encyclopedia
I never said that his number was accurate. What I said is that it's unlikely that his engine would not run at an AFR of 18:1. If it was a carbed engine then yes (because of the uneven fuel distribution that is typical of carbed engines) 18:1 would be difficult to attain without rough running or missing.

And yes, I do much leaner than stoichiometric (14.7:1) all the time when running a 360CI, magneto timed (fixed @25BTDC) air-cooled flat 4 with the throttle wide open. Can you guess the application?

What do you think happens to the combustion event as the mixture goes lean of Stoic? Given that Stoic is the theoretical perfect mix of O2 to fuel. Is having having more O2 some how more combustible? The fastest burn of the most fuel happens just a tad rich of stoic as does the highest internal cylinder pressure thereby giving the lowest detonation margins (not good). At full throttle, this is not where you want the mixture to be. You want to be richer or leaner, but since we are limited by atmospheric pressure with N/A engines and turbine inlet temp with turbocharged engines, it's far easier and practical just to puke gas through it to slow (relatively speaking) the combustion event and cool the exhaust gasses thereby increasing detonation margins.

BTW the whole reason behind direct injection is to improve fuel distribution to allow very lean mixtures. In theory this will eliminate the need for a throttle body and the suction losses associated with partial throttle operation. Imagine sucking through a straw with partially cocked butterfly valve; that's what your engine is doing whenever it's not at full throttle. With lean burn engines, the engine management system will just reduce fuel flow, the mixture will get leaner and the engine will produce less power, no suction loss from choking off the intake. Another benefit is little to no unburned hydrocarbons, meaning we may have catless road going cars in our future.

I could go on, but I'm digressing! So to come back to the original point, an injected otto cycle engine should run still run at an efficiency ratio of 18:1, whether or not it will grenade in the process depends on throttle position, timing and compression ratio. The ratio in and of itself is not a death sentence... 14.7 to one is actually a hotter, higher pressure place to run

Last edited by shadrach74; 09-27-2012 at 08:12 AM.
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Old 09-26-2012, 08:33 PM   #20
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I never said that his number accurate. What I said is that it's unlikely that his engine would not run at an AFR of 18:1.
With an 11:1 compression ratio and pump gas, an m96 motor will ping like a big dog at 18:1 A/F ratio under full load on a dyno. Narrow tuning window. It may run.... for a little while.

And yes, I do much leaner than stoichiometric (14.7:1) all the time when running a 360CI, magneto timed (fixed @25BTDC) air-cooled flat 4 with the throttle wide open. Can you guess the application?
Sounds like a Lycoming 0-360 variant. A fine aircraft engine with a very wide tuning window. With an 8.5:1 compression ratio and avgas it will probably purr like a kitten at 18:1 A/F ratio. It won't be making max power though. My father was an aerospace engineer and certified aircraft mechanic. We rebuilt a few of these in our garage when I was a kid. I am guessing you still prefer to do your sea level takeoffs at full rich.
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